I have a system from Sydell. I have a scale and a tilt table to trim hooves(really saves on my back). Yes it is all steel so much heavier than aluminum, but its what I could afford. Mine is set up in the barn so I never have to move it. I am not a big person, but if need be I can move the panels by myself, heavy yes, impossible no. Our stockdog club has a D-S system, again steel but very sturdy, makes sorting sheep easy. I do believe D-S offers galvanized panels. I know there are other manufactures of handling systems but these are the two I have personal experience with and both function very well. I recommend that if you do decide to get a system, get some drop/fold down panels, they give you easier access to the sheep.

Penny,D-S Livestock makes some aluminum equipment and now all their steel equipment is hot dipped galvanized. We have a scale from them which I like. D-S is our preferred equipment company since Sheepman Supply stocks it (30min from home) and D-S is <2hrs from home which saves on shipping costs.

The equipment from Premier is galvanize steel, the solid panels are corrugated to increase strength while using thinner (lighter) steel.Mark

My back and knees are fine (I am knocking on wood) but I fit into your age bracket.
My handling system is steel and the longer components are heavy and somewhat awkward. What I have found over the years is you adapt methods of moving things, be it hay, handling equiptment, etc. You learn to use leverage a lot.
My suggestion is to find a sheep show that is close and look at the equipment that the vendors bring in.
You may also see if there are people with systems close to you that you can look at and possibly see if you can move parts of the systems.
I personally do not like any panels that are made with tubing . I found that cattle trash the tubular panels, but the square or " U" has held up for years.
Good luck,
Suki